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<div>Hi Richard,</div><div>In other halls this kind of data is writen to data files usind CODA DAQ.</div><div>I believe we also have that capability.</div><div>Hovanes</div><div><br></div><div><br></div><div><br></div><div id="composer_signature"><div style="font-size:85%;color:#575757">Sent from my Samsung Galaxy Tab® S</div></div><br><br>-------- Original message --------<br>From: Richard Jones <richard.t.jones@uconn.edu> <br>Date: 1/11/18 1:39 PM (GMT-05:00) <br>To: Hovanes Egiyan <hovanes.egiyan@gmail.com> <br>Cc: halld-online@jlab.org <br>Subject: Re: [Halld-online] question about scalers in the EPICS archiver <br><br><div dir="ltr">Hello Hovanes and all,<div><br></div><div>This entails a serious loss of precision for long-running tallies. Essentially it means that all we have in EPICS are one-second snapshots every once in a while, between which the values can wander by 3% without any record of having done so. This makes them useless for any kind of normalization, which is what I was hoping to get from them. Suppose I wanted to get the total number of counts accummulated by a scaler over a several hour period, is there any way to get that information from anywhere in our online system right now?</div><div><br></div><div>-Richard</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jan 11, 2018 at 1:28 PM, Hovanes Egiyan <span dir="ltr"><<a href="mailto:hovanes.egiyan@gmail.com" target="_blank">hovanes.egiyan@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
Richard, <br>
<br>
The discriminator scalers are latched every second and the units are
Hz. Sergey Furletov <br>
runs the server that reads the values out into shared memory, so I
do not know the details. I believe <br>
that the value is non-integral because it gets normalized to a clock
to get rates more precisely in Hz. So <br>
the square root of the value in the DB for the scaler should be a
good estimate of the statistical error. <br>
<br>
Archiving of the scalers in MYA (or other PVs) has a deadband (for
this particular variable it is <br>
3*sqrt(value)+0.03*value), which means that if the next reading
(which is indicated by a change in <br>
the value of the EPICS variable) is within that deadband of the
latest recorded value then it does not get <br>
recorded. So, if you stripchart an EPICS variable live, you will see
a lot more frequent value changes <br>
compared to what you see when you look at the archive chart of the
same variable. <br>
This is done to reduce the update rate in the DB, otherwise it would
cost a lot more money to keep all <br>
variables in the DB without any deadbands. The deadbnads are
adjustable though, I can request smaller <br>
deadbands for a small subset of variables. <br>
<br>
Hovanes <br><div><div class="h5">
<br>
<p><br>
</p>
<br>
<div class="m_-242959757836314497moz-cite-prefix">On 01/11/2018 12:41 PM, Richard Jones
wrote:<br>
</div>
</div></div><blockquote type="cite"><div><div class="h5">
<div dir="ltr">Hello Hovanes and all,
<div><br>
</div>
<div>I am accessing the GlueX scalers in the EPICS archive using
the MYA interface, and have run into a question. I am looking
at a variable like <span>TAGM:T:8:scaler_t1
whose name suggests that it is the discriminator scaler for
TAGM column 8. When I look at the numbers in that variable,
they are obviously not scalers. They are non-integer values
in the range of 3000-8000 for the runs that I am looking at.
Are they rates? In what units? kHZ? What is the sampling
interval? This matters because of statistical error. I see
entries in there sometimes separated by tens of seconds
during a run. In the time between the samples, were the
scalers free-running so that I have the full statistical
information in the one reading at the end of the interval,
or are all of the statistics during the seconds in between
the records in the DB lost?</span></div>
<div><span><br>
</span></div>
<div><span>-Richard
J.</span></div>
</div>
<br>
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